Dafney scored a season-high 17 points, Gretzky added 16 and Simpson never trailed.
The duo shot a combined 13-for-20 from the field as the Storm (4-18, 2-9 Iowa Conference) snapped a six-game losing streak, keeping their hopes for a berth in the conference tournament alive in the process.
Nick Webber came off the bench to score 15 points for the Knights (11-11, 5-6).
Simpson scored the first nine points of the game and built a 12-point lead at halftime by outscoring Wartburg 13-4 in the final 6:03 of the half.
Back-to-back 3s by Gretzky gave Simpson its largest lead of the game, 47-31 with 13:38 left in the second.
Simpson led by 12 with just over a minute left before Wartburg was able to cut the lead to four with 14 seconds left. Ryan Olson made three free throws to seal the win.
The Storm return to action on Saturday when they host Coe at 4 p.m. on Senior Recognition Day. The Kohawks (10-12, 2-9) - who also have an outside shot at making the league tournament - beat Luther on Wednesday. Coe won the first meeting 68-54.